This application relates to functionally graded cemented tungsten carbide materials that contain a cobalt gradient. These materials may be abbreviated as WC—Co materials. Such materials may be used for metal cutting tools, rock drilling tools for oil exploration, mining, construction and road working tools and many other metal-working tools, metal-forming tools, metal-shaping tools, and other applications. For background information, the reader should consult U.S. Patent Application Publication No. 2005/0276717, which patent application is expressly incorporated herein by reference.
As explained in the prior patent publication noted above, it is desirable to construct a cemented tungsten carbide material (“WC” material) that includes an amount of cobalt. These materials are referred to as WC—Co materials. It is desirable to construct a WC—Co material that has a combination of toughness and wear-resistance.
Cemented tungsten carbide (WC—Co), consisting of large volume fractions of WC particles in a cobalt matrix, is one of the most widely used industrial tool materials for metal machining, metal forming, mining, oil and gas drilling and all other applications. Compared with conventional cemented WC—Co, functionally graded cemented tungsten carbide (FGM WC—Co) with a Co gradient spreading from the surface to the interior of a sintered piece offers a superior combination of mechanical properties. For example, FGM WC—Co with a lower Co content in the surface region demonstrates better wear-resistance performance, resulting from the combination of a harder surface and a tougher core. Though the potential advantages of FGM WC—Co are easily understood, manufacturing of FGM WC—Co is however a difficult challenge. Cemented WC—Co is typically sintered via liquid phase sintering (LPS) process in vacuum. Unfortunately, when WC—Co with an initial cobalt gradient is subjected to liquid phase sintering, migration of the liquid Co phase occurs and the gradient of Cobalt is easily eliminated.